President Donald Trump started his term as the Detroit auto industry’s best friend in at least a generation. His policies since then suggest reality can be more complex.

The Trump administration’s proposals on fuel economy and trade — with Canada and Mexico, with China, and maybe with special barriers to foreign-made vehicles imported into the United States — threaten to upend delicate balances the industry has spent years refining, analysts and ranking officials say.

“One always has to be aware of the unintended consequences,” said U.S. Rep. Debbie Dingell, D-Dearborn. Speaking about the president’s relationship with automakers, she said, “I know how complicated the issues are, and I know how complicated the man is.”

Sweeping change to crucial trade relationships, as well as an easing of Obama-era fuel-economy rules, could offer the automakers an opportunity to help shape their future under a new administration. That’s partly because their manufacturing workforces are so clustered in the politically important industrial Midwest. But it’s too soon, officials say, to predict final results.

A global supply network could be disrupted, driving costs higher. An administration proposal to slap special conditions on foreign imports into the United States — so-called “non-tariff barriers” successive American administrations have condemned — threaten not just vehicles imported by German and Italian, Japanese and South Korean rivals. They invite retaliation from their respective governments.

Non-tariff barriers ostensibly designed to ensure compliance with U.S. emissions standards theoretically could target Buicks built in China, South Korea and Germany. They also could target small trucks and SUVs made by Ford Motor Co. in Spain and India — all sold in U.S. showrooms to American consumers who likely would face higher prices.

Fiat Chrysler Automobiles NV builds U.S.-bound Fiat models in Italy, Serbia and Japan. It assembles Alfa Romeo-brand cars in Italy, and produces Ram-brand cargo vans built in Turkey. Altogether, roughly 60 percent of the vehicles bought annually by American consumers carry foreign nameplates, a meaningful chunk of which are built in foreign-owned U.S. plants.

“It’s a little bit more complex than I think Trump saw, because the domestic automakers bring stuff in from other parts of the world,” said David Cole, chairman emeritus of the Ann Arbor-based Center for Automotive Research. “It’s sort of a way of life. This is a classic example where there seems to be sort of an obvious thing to do: let’s penalize the international guys and that will help the domestic guys. Well, maybe not.”

And the rhetoric about “rolling back” existing federal fuel economy rules, coming chiefly from the embattled Environmental Protection Agency administrator, Scott Pruitt, is not sitting well with automakers who say they do not want a rollback.

They say they’re seeking modernization of fuel-economy standards that take into account trends toward hybrids and electrification, autonomy and ride-sharing. Even as they expand their truck and SUV lineups, Detroit’s automakers are investing heavily in electrification and trying to rebuild their cred with coastal consumers in some of the country’s largest markets.

Details matter. Less than 15 months into the Trump administration, automakers are beginning to understand the president’s bargaining style: identify a seemingly intractable problem, take a maximum position intended to draw strong reaction, be open to making adjustments and work back from there.

They also understand, according to ranking officials, that there is no benefit to publicly contradicting or challenging administration proposals — a position industry officials reiterated in interviews with The Detroit News. Public push-back risks not only a presidential backlash on Twitter; it could impede a communication back-channel used by the administration and the industry to share policy ideas and to explain the complexity of the interconnected industry.

Last Friday, The Wall Street Journal reported that the administration’s trade office is exploring how and whether to erect special, or “non-tariff,” barriers for foreign-made vehicles. The idea under discussion, confirmed by The News: foreign-made vehicles would be subject to stricter environmental controls not technically considered tariffs — precisely the kind of unilateral action Washington long criticized in its trading partners, especially Japan and South Korea.

Global Automakers, the trade group representing 12 foreign automakers operating in the United States, called the proposal “ironic ... a bad idea and a pretext for protectionism. It will increase prices for consumers and invite retaliatory actions by other countries.”

The White House response: “China has been participating in unfair and illegal trade practices for decades,” press secretary Sarah Huckabee Sanders said in a statement. “The President has the backbone and strength to try and level the playing field for all U.S. manufacturers who have been harmed by China. He will promote free, fair and reciprocal trade practices to grow the U.S. economy.”

Growing talk of a trade war with China has worried investors and sparked market sell-offs — until Tuesday. That’s when China’s president, Xi Jinping, used a speech at the Boao Forum for Asia to signal that China would “significantly lower” tariffs this year and ease restrictions on foreign ownership in China’s massive auto industry, The Associated Press reported.

China’s promised tariff reduction on American-made metal arguably could be a hollow victory, however. Last year, General Motors Co. imported just 200 Chevrolet Camaros into China, it said, but Detroit’s No. 1 automaker and its joint-venture partners sold slightly more than 4 million China-built vehicles to Chinese consumers.

In a tweet, President Trump replied: “Very thankful for President Xi of China’s kind words on tariffs and automobile barriers ... also, his enlightenment on intellectual property and technology transfers. We will make great progress together!”

Any auto company exporting from China to the United States currently pays a 2.5 percent tariff on cars and a 25-percent levy on trucks, the so-called “Chicken Tax” established in the 1960s that long ago dropped levies on chicken that still apply to light trucks. By contrast, imports of American-made vehicles into China get slapped with a 25-percent tariff — or twice that, should China make good on recent tariff threats.

“I don’t think the Chinese automotive industry needs protection,” said Joe Phillippi, principal of New Jersey-based AutoTrends Consulting. “It’s awfully mature, not just in terms of volume but in terms of their overall levels of manufacturing expertise.”

Still, Phillippi and others say, an all-out trade war isn’t good for anyone: “We run the risk of being hurt the most if the Chinese really decide they want to come down hard on our relationship with their (joint-venture) partners.

“They could make life very difficult for U.S. companies if they wanted to by putting a lot of pressures on the car companies themselves and perhaps pressuring the market infrastructure, meaning the dealer bodies. There could be pressure to de-emphasize American brands.”

That’s an especially acute fear for automakers like GM, whose No. 1 market in terms of sales (not profitability) is China. Its ties to its Chinese joint-venture partners, as well as its relationships with Chinese regulators and government officials, could be adversely impacted by an escalating trade war exacerbated by tough public talk.

“There’s a historical perspective that hasn’t been adjusted,” Cole said. “You have a picture in your mind of what the industry is now being what it was. And they’re different. There’s potential here to do something stupid because you don’t understand the bigger picture.”